Are there actually already both: (⛽= petrol and diesel heaters) for the: (🌍=worldwide) households on our: (🌍=Earth=World)?
"I know from my own experience that there are already both: (gas, wood and oil heating systems)" , "but are there already both: (petrol and diesel heating systems???") "Therefore, my above research question, intellectual question, social question, or knowledge question, is truthful…"